We propose to continue studies on the range of lymphokine activities, the kinds of cells that can produce lymphokines, and on the mechanism of lymphokine action. Specific attention will be paid to regulation and control of these activities. The factor produced by T cells which suppresses the ability of B cells to generate such mediators as migration inhibition factor (MIF) will be characterized and its mechanism of action explored. Concurrently, we will explore the possibility that MIF production is also under feedback control, and that MIF itself may suppress further production of MIF. These latter studies will involve passive administration of exogeneous mediator, taking advantage of the different molecular forms of MIF that are found in the guinea pig. In addition, we will focus attention on possibilities for suppressing the biologic activity of lymphokines by techniques involving either inhibition by monosaccharides or other simple compounds, or by techniques that involve direct modification of the lymphokine molecule itself. These studies will be performed in order to explore new and potentially clinically exploitable procedures for manipulating a specific aspect of the immune response, involving the effector component of cell-mediated immunity.